Evaluate the initial safety and effectiveness of Microburst VNS stimulation in subjects with refractory epilepsy.

Inclusion Criteria:

1. Clinical diagnosis of medically refractory epilepsy with primary generalized tonic-clonic seizures (limited to 20 subjects) or partial onset seizures including complex partial seizures with or without secondary generalization (limited to 20 subjects).
2. Must be on adjunctive antiepileptic medications.
3. Willing and capable to undergo multiple evaluations with functional magnetic resonance imaging (fMRI), electroencephalogram (EEG) and electrocardiogram (ECG).

4(A) For subjects with partial onset seizures: An average of ≥ 3 countable seizures per month based on seizure diary during the 3 month baseline period and no seizure-free interval greater than 30 days during those 3 months.

4(B) For subjects with PGTCs: Have at least ≥ 3 countable seizures during the 3 month baseline period. Note: Each seizure within a cluster may be counted as separate seizures.

5. 12 years of age or older.

6. Subject is a male or non-pregnant female adequately protected from conception. Females of childbearing potential must use an acceptable method of birth control.

7. Provide written informed consent-assent/Health Insurance Portability and Accountability Act (HIPAA) authorization and self-reported measures with minimal assistance as determined by the investigator.

Exclusion Criteria:

1. Currently using, or are expected to use, short-wave diathermy, microwave diathermy, or therapeutic ultrasound diathermy.
2. A VNS Therapy System implant would (in the investigator's judgment) pose an unacceptable surgical or medical risk for the subject.
3. A planned procedure that is contraindicated for VNS therapy.
4. History of implantation of the VNS Therapy System.
5. Currently receiving treatment from an active implantable medical device.
6. Presence of contraindications to MRI per the MRI subject screening record.
7. Known clinically meaningful cardiovascular arrhythmias currently being managed by devices or treatments that interfere with normal intrinsic heart rate responses (e.g., pacemaker dependency, implantable defibrillator, beta adrenergic blocker medications).
8. History of chronotropic incompetence (commonly seen in subjects with sustained bradycardia [heart rate < 50 bpm]).
9. Cognitive or psychiatric deficit that in the investigator's judgment would interfere with the subject's ability to accurately complete study assessments.
10. History of status epilepticus within 1 year of study enrollment.
11. Dependent on alcohol or narcotic drugs as defined by DSM IV-TR within the past 2 years, based on history. Tests for drug or alcohol use will not be administered.
12. Currently being treated with prescribed medication that contains cannabis or cannabis related substance including recreational use.
13. Any history of psychogenic non-epileptic seizures.
14. Currently participating in another clinical study without LivaNova written approval.